Rotator Cuff-Quadrangular Space-Rotator Cuff Tendinitis-Rupture of the Supraspinatus Tendon-Arterial Anastomosis around the Shoulder Joint-Branches from the Subclavian Artery- Branches from the Axillary Artery-Arterial Anastomosis and Ligation of the Axillary Artery

Rotator Cuff

The rotator cuff is the name given to the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles, which are fused to the underlying capsule of the shoulder joint. The cuff plays a very important role in stabilizing the shoulder joint. The tone of these muscles assists in holding the head of the humerus in the glenoid cavity of the scapula during movements at the shoulder joint. The cuff lies on the anterior, superior, and posterior aspects of the joint. The cuff is deficient inferiorly, and this is a site of potential weakness.

Quadrangular Space

The quadrangular space is an intermuscular space, located immediately below the shoulder joint. It is bounded above by the subscapularis and capsule of the shoulder joint and below by the teres major muscle. It is bounded medially by the long head of the triceps and laterally by the surgical neck of the humerus.

The axillary nerve and the posterior circumflex humeral vessels pass backward through this space .

Rotator Cuff Tendinitis

The rotator cuff, consisting of the tendons of the subscapularis, supraspinatus, infraspinatus, and teres minor muscles, which are fused to the underlying capsule of the shoulder joint, plays an important role in stabilizing the shoulder joint. The rotator cuff presses the humeral head into the glenoid cavity. Lesions of the cuff are a common cause of pain in the shoulder region.

Failure of the cuff is due to either wear or tear. Wear is age related. Excessive overhead activity of the upper limb may be the cause of tendinitis, although many cases appear spontaneously. During abduction of the shoulder joint, the supraspinatus tendon is exposed to friction against the acromion. Under normal conditions, the amount of friction is reduced to a minimum by the large subacromial bursa, which extends laterally beneath the deltoid. Degenerative changes in the bursa are followed by degenerative changes in the underlying supraspinatus tendon, and these may extend into the other tendons of the rotator cuff. Clinically, the condition is known as subacromial bursitis, supraspinatus tendinitis, or pericapsulitis. It is characterized by the presence of a spasm of pain in the middle range of abduction, when the diseased area impinges on the acromion. Extensive acute traumatic tears are best repaired surgically as soon as possible. Small chronic cuff injuries are best managed without surgery using nonsteroidal anti-inflammatory drugs and muscle exercises.

Rupture of the Supraspinatus Tendon

In advanced cases of rotator cuff tendinitis, the necrotic supraspinatus tendon can become calcified or rupture. Rupture of the tendon seriously interferes with the normal abduction movement of the shoulder joint. It will be remembered that the main function of the supraspinatus muscle is to hold the head of the humerus in the glenoid fossa at the commencement of abduction. The patient with a ruptured supraspinatus tendon is unable to initiate abduction of the arm. However, if the arm is passively assisted for the first 15° of abduction, the deltoid can then take over and complete the movement to a right angle
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Arterial Anastomosis around the Shoulder Joint

The extreme mobility of the shoulder joint may result in kinking of the axillary artery and a temporary occlusion of its lumen. To compensate for this, an important arterial anastomosis exists between the branches of the subclavian artery and the axillary artery, thus ensuring that an adequate blood flow takes place into the upper limb irrespective of the position of the arm

Branches from the Subclavian Artery

■■ The suprascapular artery, which is distributed to the supraspinous and infraspinous fossae of the scapula

■■ The superficial cervical artery, which gives off a deep branch that runs down the medial border of the scapula

 Branches from the Axillary Artery

■■ The subscapular artery and its circumflex scapular branch supply the subscapular and infraspinous fossae of the scapula, respectively.

■■ The anterior circumflex humeral artery

■■ The posterior circumflex humeral artery Both the circumflex arteries form an anastomosing circle around the surgical neck of the humerus.

Arterial Anastomosis and Ligation of the Axillary Artery

The existence of the anastomosis around the shoulder joint is vital to preserving the upper limb should it be necessary to ligate the axillary artery.